Phanogomphus lividus exuvia

April 5, 2018

The Backstory

An Ashy Clubtail dragonfly (Phanogomphus lividusnymph was collected by Bob Perkins. (The date and location where the specimen was collected are unknown.) The nymph was reared in captivity until it emerged on 21 March 2017 and metamorphosed into an adult female. This specimen is the exuvia from the nymph. P. lividus is a member of the Family Gomphidae (Clubtails).

A two-step process was used to verify the identity of the exuvia.

  1. Determine the family.
  2. Determine the genus and species.

Step 1. Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video Identifying dragonfly larva to family (8:06). Here’s the decision tree used to identify the exuvia as a member of the Family Gomphidae (Clubtails).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in Photo No. 1 and 3.
  • Antennae are club-like (not thin and thread-like, as in  Aeshnidae larvae), as shown in Photo No. 1.

It’s simple and straightforward to recognize this specimen is a clubtail.

No. 1 | Ashy Clubtail (Phanogomphus lividus) | exuvia (face-head)

Step 2. Genus and species

Lateral spines are present on abdominal segments six through nine (S6-S9).

The superior caudal appendage (epiproct) is as long as inferiors (paraprocts), as shown in Photo No. 4. The view of the terminal appendages is still slightly obscured by debris after the specimen was cleaned, making it challenging to distinguish the cerci from the paraprocts. Nonetheless, the epiproct and paraprocts appear to be nearly the same length.

The median lobe of the labium (prementum) is straight-edged, as shown in Photo No. 5.

After emergence

The next photograph shows the Ashy Clubtail dragonfly after emergence from one of Bob Perkins‘ holding tanks. Phanogomphus lividus is 48-56 mm in total length (Paulson, 2011).

Image used with permission from Bob Perkins.

This individual is a female, as indicated by its rounded hind wings and terminal appendages.

Image used with permission from Bob Perkins.

Related Resource

The dichotomous key for Gomphus (now Phanogomphus) that appears on p. 20 in Identification Keys to Northeastern Anisoptera Larvae, compiled by Ken Soltesz, was used to attempt to verify the genus and species of the exuvia. Markers that match this specimen are highlighted in boldface green text. Three boldface green asterisks (***) are used to highlight the thread for identification of P. lividus. Disclaimers are highlighted in boldface red text.

1a. Lateral spines on abdominal segments 7 to 9 (very minute if present on 6). [2]
***1b. Lateral spines on abdominal segments 6 to 9 well developed. [3]

3a. Superior caudal appendage (epiproct) shorter than inferiors (paraprocts); Teeth on lateral lobes of labium obsolete or poorly developed. [quadricolor]
***3b. Superior caudal appendage (epiproct) as long as inferiors (paraprocts); Teeth on lateral lobes of labium well developed. [4]

***4a. Median lobe of labium straight-edged. [lividus]
4b. Median lobe of labium convex-edged. [5]


Note: The weakest aspect of this key is couplet 4, as it applies to Gomphus descriptus [Harpoon Clubtail], the difference in the “convexity” of the median lobe between lividus and descriptus being very slight and difficult to discern in practice. Donnelly (pers. comm.) has found that, at least with New York specimens, the posterior narrowing of the median lobe of the labium is more abrupt in livid, and relatively gradual in descriptus. Also, the labial teeth are better developed in livid than in descriptus. These characters are so relative that any unknown suspected of being either of these species should be compared to reference specimens.

Tech Tips

The following equipment was used to shoot Photo No. 2 and 3: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. Photo No. 1, 4, and 5Canon MP-E 65mm Macro lens (manual focus only, set for either 2x or 3x magnification) plus the multiple-flash setup.

Photo No. 1-3 are focus-stacked composite images created and annotated using Adobe Photoshop CC 2017.

Bob Perkins’ photos were shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.

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Refinements in focus stacking workflow

April 3, 2018

By trial and error, I’m slowly refining the workflow that I use to create focus-stacked composite images. My goal is maximizing efficiency while minimizing unexpected results. I’m planning to publish a step-by-step “how to” tutorial after my workflow is honed to perfection. Hah! I’m not sure that’s attainable, but I’m working on it.

In the meantime, here are two more composite images created using the latest refinements in my focus stacking workflow.

Both composite images were created from three photos: one focused on the head/prementum; another focused on the middorsal body; and the last focused on the anal pyramid (terminal appendages).

I started using the High Pass filter in Photoshop to sharpen images and I am pleased with the results.

Sharpening doesn’t fix out-of-focus areas, such as the far hind leg in both images. I’m not sure what the “sweet spot” is for the Canon 100mm macro lens; the consensus seems to be photos are sharpest at f/8. I shoot at f/22 for single images with one focus point. I have been testing f/18 for the two- and three-photo focus stacks published recently, but as you can see, I should probably add a fourth photo focused on the farthest part of the subject.

The Backstory

An Ashy Clubtail dragonfly (Phanogomphus lividusnymph was collected by Bob Perkins. (The date and location where the specimen was collected are unknown.) The nymph was reared in captivity until it emerged on 21 March 2017 and metamorphosed into an adult female. This specimen is the exuviafrom the nymph. P. lividus is a member of the Family Gomphidae (Clubtails).

Tech Tips

The following equipment was used to shoot all three photos in the composite image: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode; and Canon 580 EX- and Canon 580EX II Speedlites in “Slave” mode.

Adobe Photoshop CC 2017 was used to create the composite images by “round-tripping” with Apple Aperture. Although the round-trip has a few detours in my experimental workflow, there are fewer unpleasant surprises along the way. Worth the extra steps, in my opinion.

Copyright © 2018 Walter Sanford. All rights reserved.

Ashy Clubtail dorsal view composite

April 1, 2018

One look at the unusual filename of the following image, and you know it’s a composite of three photos: one focused on the head; another focused on the middorsal body; and the last focused on the anal pyramid (terminal appendages).

The results appear to be worth the extra time and effort to create a high-quality image of a beautiful specimen.

The Backstory

An Ashy Clubtail dragonfly (Phanogomphus lividusnymph was collected by Bob Perkins. (The date and location where the specimen was collected are unknown.) The nymph was reared in captivity until it emerged on 21 March 2017 and metamorphosed into an adult female. This specimen is the exuviafrom the nymph. P. lividus is a member of the Family Gomphidae (Clubtails).

Tech Tips

The following equipment was used to shoot all three photos in the composite image: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode; and Canon 580 EX- and Canon 580EX II Speedlites in “Slave” mode.

Adobe Photoshop CC 2017 was used to create the composite image by “round-tripping” with Apple Aperture.

Copyright © 2018 Walter Sanford. All rights reserved.

Ashy Clubtail exuvia focus stack

March 30, 2018

The Backstory

An Ashy Clubtail dragonfly (Phanogomphus lividus) nymph was collected by Bob Perkins. (The date and location where the specimen was collected are unknown.) The nymph was reared in captivity until it emerged on 21 March 2017 and metamorphosed into an adult female. This specimen is the exuvia from the nymph. P. lividus is a member of the Family Gomphidae (Clubtails).

Tech Tips

The preceding image is a composite of 39 photos taken using the following equipment: Canon EOS 5D Mark II digital camera, in manual mode; Canon MP-E 65mm Macro lens (manual focus only, set for 3x magnification); and Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode.

Adobe Photoshop CC 2017 was used to focus stack the photos and post-process the final output.

According to the “Focus Stacking Step Size Calculator” embedded in the “Focus Stacking” Web page, the “safe step size” is 0.213 mm for an aperture of f/11 at 3x magnification using a full-frame DSLR. That’s right, 0.213 mm! The safe step size is the incremental distance at which the in-focus areas of two photos overlap. The ruler on the inexpensive focus rail that I use is marked in millimeters only, so I attempted to move the focus rail in tiny increments in two passes: one pass moving from front-to-back; and a second pass from back-to-front.

Copyright © 2018 Walter Sanford. All rights reserved.

Previews of coming attractions

March 28, 2018

Several test photos were taken for an upcoming identification guide for exuviae from Slaty Skimmer dragonfly (Libellula incesta).

The exuvia has a mask-like labium with smooth crenulations, indicating this specimen is a member of the Family Libellulidae (Skimmers), the largest family of dragonflies.

No. 1 | Libellula incesta | exuvia (face-head-dorsal)

Also notice the exuvia has “pointed” eyes, rather than “rounded” eyes like the exuvia from a Carolina Saddlebags dragonfly (Tramea carolina) shown below.

No. 2 | Tramea carolina | exuvia (face-head)

The pointed- versus rounded eyes dichotomy is a somewhat subjective decision, but if you make the right choice then this marker can be used to narrow the range of possible Libellulidae genera.

Exuviae from three genera of Libellulidae have pointed eyes: Libellula (18 species); Orthemis (3 species); and Plathemis (2 species). Slaty Skimmer (Libellula incesta) is one of 18 species in the genus Libellula.

Exuviae from all other genera of Libellulidae have rounded eyes.

No. 3 | Libellula incesta | exuvia (dorsal)

This specimen needs to be rehydrated/relaxed in order to remove some distracting debris and reposition the legs for better photo poses.

No. 4 | Libellula incesta | exuvia (ventral)

To be continued…

The Backstory

A Slaty Skimmer dragonfly (Libellula incesta) nymph was collected by Bob Perkins on 29 May 2017 along Pine Creek in Carroll County, Virginia USA. The nymph was reared in captivity until it emerged on 29 June 2017 and metamorphosed into an adult male. This specimen is the exuvia from the nymph.

Copyright © 2018 Walter Sanford. All rights reserved.

Ophiogomphus incurvatus exuvia

March 26, 2018

Disclaimer

Soon after I began creating illustrated identification guides for odonate exuviae, I shared a pointer to Perithemis tenera exuviae on the Northeast Odonata Facebook group. Ed Lam commented on my post. The operative sentence is as follows.

I don’t expect anyone to identify Perithemis tenera larvae from Walter’s blog post but it gives a novice a better sense of what larval identification is all about and that has value. Source Credit: Ed Lam, Northeast Odonata Facebook group.

I disagree with Ed’s comment, although I let it go at the time in deference to Ed’s considerable expertise. I do expect anyone can use my guides to identify the species of odonate featured in each guide. Otherwise, what’s the point of making the guides? After I read Ed’s comment I tweaked the specific blog post and retooled the template that I use for most guides.

All of that being said, in my opinion it would be challenging at best to identify an exuvia from Ophiogomphus incurvatus to the species level using only the dichotomous key in Dragonflies of North America by Needham et al., the best resource currently available — significant sections of the key are unclear and unreliable. In contrast, Bob Perkins and I know the identity of the specimen because Bob observed the species of adult dragonfly that emerged from the exuvia.

For what it’s worth, this blog post features a fairly complete set of annotated photos of an Ophiogomphus incurvatus exuvia. Perhaps the photo set can be used in combination with the dichotomous key in order to make identification easier for others.

The Backstory

An Appalachian Snaketail dragonfly (Ophiogomphus incurvatus) nymph was collected by Bob Perkins. The nymph was reared in captivity until it emerged on 20 March 2017 and metamorphosed into an adult male. This specimen is the exuvia from the nymph. Appalachian Snaketail is a member of the Family Gomphidae (Clubtails).

A two-step process was used to attempt to verify the identity of the exuvia.

  1. Determine the family.
  2. Determine the genus and species.

Step 1. Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video Identifying dragonfly larva to family (8:06). Here’s the decision tree used to identify the exuvia as a member of the Family Gomphidae (Clubtails).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in Photo No. 1, 5, and 6.
  • Antennae are club-like (not thin and thread-like, as in  Aeshnidae larvae), as shown in Photo No. 1.

It’s simple and straightforward to recognize this specimen is a clubtail. Expect a bumpy ride beyond this point!

No. 1 | Ophiogomphus incurvatus | exuvia (face-head)

Step 2. Genus and species

The size of specific antennal segments is a significant marker for identifying some species of Ophiogomphus. In this case, the antennae on the specimen will need to be cleaned in order to count segments and measure their dimensions.

No. 2 | Ophiogomphus incurvatus | exuvia (dorsal)

Lateral spines are present on abdominal segments seven through nine (S7-S9). Dorsal hooks appear to be well developed on segments eight and nine (S8, S9); they resemble “dorsal abdominal processes” on most other abdominal segments.

No. 3 | Ophiogomphus incurvatus | exuvia (dorsal-lateral)

The cerci are approximately three-fourths (3/4) as long as the epiproct and paraprocts.

No. 4 | Ophiogomphus incurvatus | exuvia (anal pyramid)

Photo No. 4 and 5 show ventral views of the exuvia.

No. 5 | Ophiogomphus incurvatus | exuvia (ventral)

The vestigial hamules shown in both photos indicate this individual is a male.

After emergence

The next photograph shows the Appalachian Snaketail dragonfly after emergence from one of Bob Perkins‘ holding tanks. Ophiogomphus incurvatus is 40-43 mm in total length (Paulson, 2011).

Image used with permission from Bob Perkins.

This individual is a male, as indicated by its “indented” hind wings, hamules, and terminal appendages.

Image used with permission from Bob Perkins.

Related Resource

The dichotomous key for Ophiogomphus that appears on pp. 261-262 in Dragonflies of North America, Third Edition by Needham et al. was used to attempt to verify the genus and species of the exuvia. Markers that match this specimen are highlighted in boldface green text. Three boldface green asterisks (***) are used to highlight the thread for identification of O. incurvatus. Disclaimers are highlighted in boldface red text.

p. 261

1. Abdomen without lateral spines or dorsal hooks; antennal segment 4 minute, much narrower than segment 3. [howei]
***1’. Lateral spines present on abdominal segments 6 or 7-9; dorsal hooks usually well developed, if vestigial then antennal segment 4 more than 1/2 as wide as segment 3. [2]

2(1’). Antennal segment 4 more than 1/2 as wide as segment 3 (Fig. 319a); dorsal hooks on abdominal segments 2-9 low and blunt, or vestigial. [3]
***2’. Antennal segment 4 minute, much less than 1/2 as wide as segment 3; dorsal hooks normally prominent, usually hook-like, on at least some of abdominal segments 2-9 (sometimes low in O. carolus). [4]

p. 262

4(2’). Lateral spines on abdominal segments 6-9 (Fig. 323d). [5]
***4’. Lateral spines on abdominal segments 7-9 only. [6]

***6(4’). Dorsal hooks on abdominal segments 2-4 in lateral view usually less than 2/3 as high (measured from lowest point at intersegmental margin) as dorsal length of their respective tergites (along sclerotized, granulated cuticle only), in dorsal view with obtuse apices not extending backward beyond posterior border of tergite (Fig. 322a). [7*]
6’. Dorsal hooks on abdominal segments 2-4 in lateral view 2/3 as high, or more, (measured as above) as dorsal length of their respective tergites, in dorsal view with acute apices extending backward beyond posterior border of tergite (not beyond smooth intersegmental membrane; Fig. 322e). [14*]

***7(6). Antennal segment 3 not more than twice as long as wide. [8**]
7’. Antennal segment 3 is 2.3 to 3.0 times as long as wide. [10**]

***8(7). Antennal segment 3 is 1.7 to 1.8 times as long as wide; dorsal abdominal hooks highest and subequal on segments 2 or 3 to 4 or 5. [incurvatus**]
8’. Antennal segment 3 is 1.8 to 2.0 times as long as wide; dorsal abdominal hooks highest and subequal on segments 2 and 3 (Fig. 322a). [9**]


* Interpretation of this couplet in some individual cases may be ambiguous; if in doubt try both choices.
** Separation based on antennal measurements may be difficult in practice. Careful attention to shape of antennal segments (Fig. 319) should also help.

Tech Tips

The following equipment was used to shoot Photo No. 2, 3, and 5: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. Photo No. 1, 4, and 6Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification) plus the multiple-flash setup.

Adobe Photoshop CC 2017 was used to annotate Photo No. 1-6Photo No. 2, 4, 5, and 6 are focus-stacked composite images.

Bob Perkins’ photos were shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.

More composite images

March 24, 2018

Adobe Photoshop CC 2017 was used to create two simple two-image focus stacks. The composite images are perfectly in focus from head-to-tail.

Photo No. 1 is a composite image of two photos: one photo focused on the head; another photo focused on the anal pyramid.

No. 1 | 100mm | ISO 100 | f/22 | 1/500s | 0 ev

Photo No. 2 is a composite image of two photos: one photo focused on the prementum; another photo focused on the anal pyramid.

No. 2 | 100mm | ISO 100 | f/22 | 1/500s | 0 ev

The Backstory

An Appalachian Snaketail dragonfly (Ophiogomphus incurvatus) nymph was collected by Bob Perkins. The nymph was reared in captivity until it emerged on 20 March 2017 and metamorphosed into an adult male. This specimen is the exuvia from the nymph. Appalachian Snaketail is a member of the Family Gomphidae (Clubtails).

Tech Tips

The following equipment was used to shoot both photos in the composite image: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode; and Canon 580 EX- and Canon 580EX II Speedlites in “Slave” mode.

Adobe Photoshop CC 2017 was used to create the composite image by “round-tripping” with Apple Aperture.

Copyright © 2018 Walter Sanford. All rights reserved.

Head-to-head, reprise

March 22, 2018

Head shots of an odonate exuvia from an Appalachian Snaketail dragonfly (Ophiogomphus incurvatus) were taken using two macro lenses: Canon EF100mm f/2.8L Macro lens (smallest aperture = f/32); Canon MP-E 65mm Macro lens (smallest aperture = f/16).

No. 1 | Canon EF 100mm Macro lens | f/22

Although there is more depth of field at f/22 than f/16, the more dramatic shot appears to be the one taken at higher magnification (2x) using the Canon MP-E 65mm Macro lens (shown below). Which photo do you prefer?

No. 2 | Canon MP-E 65mm Macro lens | f/16

The Backstory

An Appalachian Snaketail dragonfly (Ophiogomphus incurvatus) nymph was collected by Bob Perkins. The nymph was reared in captivity until it emerged on 20 March 2017 and metamorphosed into an adult male. This specimen is the exuvia from the nymph. Appalachian Snaketail is a member of the Family Gomphidae (Clubtails).

Tech Tips

The following equipment was used to shoot Photo No. 1: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. Photo No. 2Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification) plus the multiple-flash setup.

Apple Aperture and Adobe Photoshop CC 2017 were used to edit both images.

Copyright © 2018 Walter Sanford. All rights reserved.

Ophiogomphus aspersus exuvia

March 20, 2018

A Brook Snaketail dragonfly (Ophiogomphus aspersusnymph was collected by Bob Perkins on either 10 SEP 2017 or 03 OCT 2017 (the date is uncertain) along the New River in southwestern Virginia. The nymph was reared in captivity until it emerged on 31 OCT 2017 and metamorphosed into an adult female. The following specimen is the exuvia from the nymph. Brook Snaketail is a member of the Family Gomphidae (Clubtails).

A two-step process was used to verify the identity of the exuvia.

  1. Determine the family.
  2. Determine the genus and species.

Step 1. Family

First, determine the family of the specimen. For reference, watch the excellent Vimeo video Identifying dragonfly larva to family (8:06). Here’s the decision tree used to identify the exuvia as a member of the Family Gomphidae (Clubtails).

  • The specimen has a flat labium that doesn’t cover the face (not mask-like), as shown in Photo No. 1, 4, and 5.
  • Antennae are club-like (not thin and thread-like, as in  Aeshnidae larvae), as shown in Photo No. 1.

No. 1 | Ophiogomphus aspersus | exuvia (face-head)

Step 2. Genus and species

The dichotomous key for Ophiogomphus that appears on p. 262 in Dragonflies of North America, Third Edition by Needham et al. was used to verify the genus and species of the exuvia. The eleventh couplet [11, 11′] is as follows.

11(10). Lateral margins of prementum slightly convergent in distal 1/2 (Fig. 320c); lateral abdominal spines about 1/8 length of lateral margin of corresponding segment; in dorsal view, cerci about 2-1/2 times as long as basal width; dorsal hooks on abdominal segments 3-6 erect (Fig. 322d). [aspersus]

11’. Lateral margins of prementum parallel or slightly divergent in distal 1/2 (Fig. 320K); lateral abdominal spines each about 1/5 length of lateral margin of corresponding segment; in dorsal view, cerci each about twice as long as basal width; dorsal hooks on abdominal segments 3-6 appressed (Fig. 322d). [rupinsulensis]

No. 2 | Ophiogomphus aspersus | exuvia (dorsal)

The word “process,” as in “dorsal abdominal process,” is defined as follows.

An upstanding prominence, usually narrow and rod-like or spine-like. Source Credit: Glossary, Dragonflies of North America.

The dorsal hooks, a.k.a., dorsal abdominal processes, on abdominal segments three through six (S3-S6) are erect. Hey, call them whatever you like, including “erect” — there are raised bumps along most of the mid-dorsal abdomen, some of which are raised more noticeably than others, as shown in Photo No. 3.

No. 3 | Ophiogomphus aspersus | exuvia (dorsal-lateral)

The next two annotated images show ventral views of the exuvia.

No. 4 | Ophiogomphus aspersus | exuvia (ventral)

The flat labium doesn’t cover the face and the lateral margins of the prementum are slightly convergent in the distal half, as shown in Photo No. 5.

No. 5 | Ophiogomphus aspersus | exuvia (prementum)

Lateral spines are present on abdominal segments seven through nine (S7-S9) only. Did I measure the length of the lateral abdominal spines to see whether they are about one-eighth (1/8) the length of the lateral margin of the corresponding segment? In a word, no — the length looks about right to my unaided eye.

The cerci are about two-and-a-half (2-1/2) times as long as their basal width. Again, the length looks about right to my unaided eye.

No. 6 | Ophiogomphus aspersus | exuvia (anal pyramid)

The rudimentary ovipositor shown in Photo No. 4 and 7 indicates this individual is a female.

No. 7 | Ophiogomphus aspersus | exuvia (rudimentary ovipositor)

After emergence

The next photograph shows the Brook Snaketail dragonfly after emergence from one of Bob Perkins‘ holding tanks. Ophiogomphus aspersus is 44-49 mm in total length (Paulson, 2011).

Image used with permission from Bob Perkins.

This individual is a female, as indicated by its rounded hind wings and terminal appendages.

Image used with permission from Bob Perkins.

The last close-up photo shows a ventral view of the subgenital plate.

Image used with permission from Bob Perkins.

Tech Tips

The following equipment was used to shoot Photo No. 2-4: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites set for “Slave” mode. Photo No. 1 and 5-7: Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification) plus the multiple-flash setup.

Adobe Photoshop CC 2017 was used to annotate selected images.

Bob Perkins’ photos were shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.

Hetaerina americana exuvia

March 18, 2018

An American Rubyspot damselfly (Hetaerina americananymph was collected by Bob Perkins on 06 August 2017 along the New River in Grayson County, Virginia USA. The nymph was reared in captivity, albeit briefly, until it emerged on 09 August 2017.

Pattern recognition can be used to tentatively identify damselfly larvae/exuviae to the family level: the shape of the prementum is characteristic for each of the three families of damselflies that occur in the mid-Atlantic region of the United States of America; mnemonics can be used to remember each distinctive shape.

Family Calopterygidae (Broad-winged Damselflies) features a prementum with a shape that looks somewhat similar to Family Coenagrionidae (Narrow-winged Damselflies). Look for an embedded raindrop shape, located toward the upper-center of the prementum.

Also notice another marker for Calopterygidae: the first antenna segment is equal to or longer than the length of the other six (6) segments added together. (Editor’s Note: Some of the smaller antennae segments are missing. It’s likely those delicate parts broke off during shipping and/or cleaning.)

No. 2 | Hetaerina americana | exuvia (ventral)

Two markers verify the genus and species of this specimen as Hetaerina americana: the labial cleft extends only to the base of the palpal lobes, as shown in Photo No. 1; and the external gills are 8.5 mm to 10 mm long (Daigle, 1991), as shown in Photo No. 2.

Before and after

Photo No. 3 shows a dorsal view of the exuvia before it was cleaned in order to remove unknown fibers covering the body and dirt/debris that obscured the labial cleft in the prementum.

No. 3 | Hetaerina americana | exuvia (dorsal)

Photo No. 1, 2 and 4 show the exuvia after cleaning. The operation appears to have been successful, other than collateral damage to two legs.

No. 4 | Hetaerina americana | exuvia (dorsal)

The next photograph shows the damselfly during emergence from one of Bob Perkins‘ holding tanks. Good timing, Bob!

Image used with permission from Bob Perkins.

The last photo shows the adult American Rubyspot damselfly sometime after emergence. Hetaerina americana is 38-46 mm in total length (Paulson, 2011). This individual is a male, as indicated by its hamules and terminal appendages.

Image used with permission from Bob Perkins.

Related Resource: Florida Damselflies (Zygoptera) – A Species Key to the Aquatic Larval Stages, by Jerrell James Daigle. Technical Series, Volume 11, Number 1, December 1991. State of Florida, Department of Environmental Regulation.

Tech Tips

The following equipment was used to shoot Photo No. 2, 3 and 4: Canon EOS 5D Mark II digital camera, in manual mode; Kenko 20mm macro automatic extension tubeCanon EF100mm f/2.8L Macro lens (set for manual focus); Canon MT-26EX-RT Macro Twin Lite. Photo No. 1 , 2 and 4: the Canon MT-26 was set for “Master” mode, and Canon 580 EX- and Canon 580EX II Speedlites were set for “Slave” mode. A Canon MP-E 65mm Macro lens (manual focus only, set for 2x magnification) plus multiple-flash setup was used for Photo No. 1.

Adobe Photoshop CC 2017 was used to annotate selected images.

Bob Perkins’ photos were shot using a Canon EOS Rebel T3i camera body and Canon EF-S 60mm macro lens.

Copyright © 2018 Walter Sanford. All rights reserved.


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